The invention relates to a housing according to the generic portion of claim 1.
Such a housing is known from DE 43 19 965 C2.
Housings of this type have been produced primarily from plastic for reasons of price and weight since the beginning of the extensive spread of mobile telephones or cordless telephones. The prefabricated, especially extruded, housing parts are coated with a conductive material to produce an electromagnetic shielding effect, possibly by spraying with conductive paint, deposition of aluminum, or galvanization. Then, a likewise shielding seal is dispensed thereon, and after insertion of the electronic function groups, the housing parts are connected to each other, usually screwed.
The shielding seal consists of an electrically conductive, elastic material and must be executed in its geometric dimensions and mechanical properties such that it adapts to surface tolerances and unevenness, such that even with the tolerances present in mass production, a very high quality of shielding of the interior of the housing is guaranteed.
Especially the beginnings, ends, and bifurcations of the seals cause problems because of the addition of system tolerances. These result from tolerances of the part (production tolerances with milling, descaling, or other tensioning or forming processes) as well as from the effect of subsequent processing (production of galvanic, mechanically applied or sprayed coatings) or other effects, such as from pressure, irradiation, heat, chemical solvents or wetting agents, etc. The production of the sealing profile with a defined height with a relatively lower tolerance is all the more critical the more miniaturized the system is. Even the achieving of adequate adherence (shear stability) is increasingly difficult in light of the addition of the tolerances and disturbing influences in miniaturized systems.
This becomes clear from the following: The dispensing element (e.g., a hollow needle) should be guided at a defined small distance (e.g., 0.6 mm) above the surface of housing part. The distance changes by 16% per 0.1 mm dimensional deviation of the housing part. Accordingly, more dispensed material would have to be applied on the surface in order to obtain a constant height of the housing part-sealing profile part system. This could be realized using an expensive measurement and control apparatus; however, such a solution is both technically and temporally impracticable in mass production.
The problems are intensified in so-called multiple-head systems with a plurality of dispensing elements which operate in parallel in a plurality of nests which have tolerance-based reaction times and must operate in coordination with each other.
Consequently, in the prior art, the system operates with an excess of material, whereby a surplus of material is applied especially at the initial, final, or connecting and bifurcation points. The sealing profiles thus produced must frequently be retouched in labor-intensive and, consequently, more expensive processes.
The object of the invention is, therefore, to provide a housing of the type mentioned which can be produced more simply and economically while meeting the tolerance specifications customary in mass production.
The object is accomplished by a housing with the characteristics of claim 1.
The invention includes the technical teaching of providing, on the housing, as an integrated component of the sealing system, a receiving area for a safety-excess of the sealing material. This enables an increase in the admissible tolerances of the housing parts as well as the control of the dispenser heads and/or the elimination of any retouching of the hardened sealing profile.
The invention provides special cost advantages when the first and/or second housing part is a cast or extruded part, especially made of plastic with the large tolerances customary therewithxe2x80x94above all when the recess serving as a receiving area is already formed in the first housing part at the time of casting or extrusion.
This receiving area mayxe2x80x94depending on the actual housing specificationxe2x80x94be arranged both in alignment with the longitudinal extension of the sealing profile and laterally offset relative thereto. It can be open on the side or closed all the way around (e.g., an open or closed hole). In the receiving area, the sealing xe2x80x9cbeadxe2x80x9d runs in certain applications preferably at angle to the direction of the further extension of the profile.
In advantageous embodiments, an incline or an edge is provided on the recess in order to achieve improved grip of the strand of sealing material with the recess during application (possibly a type of interlocking) and to counteract a possible xe2x80x9cslip offxe2x80x9d of the initial point which may occur with certain housing-seal-material pairs or with a contaminated surface.
Moreover, the recess can be formed in connection with an opening provided for the location of a connection means to connect the first and second housing parts. This configuration can also be used advantageously for an additional seal in this area.
In an additional advantageous embodiment, the recess is directly adjacent to an incompressible spacer on the surface of the first housing part protruding toward the second housing part. This is expediently formed during primary forming of the housing part from the housing material.
Currently considered the most important practical embodiment is that with an EMI-shielding and sealing profile which has an electrically conductive sealing material and with housing parts made of plastic with substantially all-over conductive coating of the surface which is in contact with the sealing profile. The invention is, however, not restricted to such shielding housings but may advantageously also be applied in dust- or watertight housings.
Advantageous improvements of the invention are also characterized in the subordinate claims or are presented in greater detail in the following along with the description of preferred embodiments with reference to the figures. They depict: